There is a wide variety of things that can cause this code. The simplest things to check for would be false air or vacuum leak. Just take a look at the air intake tube from the air cleaner to throttle body & make sure it's not loose & all hoses are attached to it. You can listen for a hissing noise coming from the intake manifold area which would indicate a vacuum leak but if there was a leak you would usually notice a running problem associated with the leak.

There are many things that can set off a lean code; defective oxygen sensor, vacuum leak(s), low fuel pressure, dirty injectors, defective injector(s) and the list goes on and on. Tests on all of these things need to be performed; as to determine what the ROOT cause for the code to set. There are a lot of people that may just replace the O2 sensor in the hope that, that was the problem. I’ve also seen a number of people that have perfectly good sensors hanging from their mirror as decoration because it didn’t fix the problem. So I guess I’m saying take the car in and have it diagnosed by someone, you feel knows how to perform the required tests. After that you can take the car home and do the repair yourself? That’s if you would even want too; once you find out what the job entails?